Engine Error

When I bring up Garry’s Mod, It begins to load the menu, Showing the background, and gets to a point where It shuts down and gives me an engine error, About how it cant load Surface properties or whatnot. I really want to test these new models I made and this is getting in the way of me and My Garrysmod. And Im just not alive without my Garry’s mod.
It says - Unable to load surface prop file ‘scripts/surfaceproperties/surfaceproperties_gmow.txt’(referenced by manifest file’ scripts/surfaceproperties_manifest.txt’)

Please help.

Isn’t gmow an addon?

I saw that somewhere. Remove that, and see if it works.